Heat a large skillet over medium-high heat. Add the ground beef and cook, breaking it into small crumbles, until fully browned (about 7-8 minutes).
Drain any excess fat from the skillet.
Add the taco seasoning and water to the beef. Stir to combine and let simmer for 5 minutes until the sauce thickens and coats the meat.
While the beef simmers, warm the taco shells according to package directions.
Fill each taco shell with seasoned beef, then top with lettuce, tomatoes, cheddar cheese, onion, and sour cream.
Squeeze fresh lime juice over the tacos and serve immediately.
Notes
Storage: Leftover seasoned beef can be stored in an airtight container in the refrigerator for up to 3 days.
For softer tacos, use flour tortillas warmed in a dry skillet.
Add diced jalapeños or hot sauce for extra heat.